InFO coil on metal plate with slot

ABSTRACT

A structure includes an encapsulating material, and a coil including a through-conductor. The through-conductor is in the encapsulating material, with a top surface of the through-conductor coplanar with a top surface of the encapsulating material, and a bottom surface of the through-conductor coplanar with a bottom surface of the encapsulating material. A metal plate is underlying the encapsulating material. A slot is in the metal plate and filled with a dielectric material. The slot has a portion overlapped by the coil.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.16/125,923, filed Sep. 10, 2018, and entitled “InFO Coil on Metal PlateWith Slot,” which is a continuation of U.S. patent application Ser. No.15/061,419, filed Mar. 4, 2016, and entitled “InFO Coil on Metal PlateWith Slot,” now U.S. Pat. No. 10,074,472 issued Sep. 11, 2018, whichclaims the benefit of the U.S. Provisional Application No. 62/267,622,filed Dec. 15, 2015, and entitled “InFO Coil and Performance ImprovementMethod,” which applications are hereby incorporated herein by reference.

BACKGROUND

With the evolving of semiconductor technologies, semiconductorchips/dies are becoming increasingly smaller. In the meantime, morefunctions need to be integrated into the semiconductor dies.Accordingly, the semiconductor dies need to have increasingly greaternumbers of I/O pads packed into smaller areas, and the density of theI/O pads rises quickly over time. As a result, the packaging of thesemiconductor dies becomes more difficult, which adversely affects theyield of the packaging.

Conventional package technologies can be divided into two categories. Inthe first category, dies on a wafer are packaged before they are sawed.This packaging technology has some advantageous features, such as agreater throughput and a lower cost. Further, less underfill or moldingcompound is needed. This packaging technology suffers from drawbacks.For example, the sizes of the dies are becoming increasingly smaller,and the respective packages can only be fan-in type packages, in whichthe I/O pads of each die are limited to the region directly over thesurface of the respective die. With the limited areas of the dies,however, the number of the I/O pads is limited due to the limitation ofthe pitch of the I/O pads. If the pitch of the pads is to be decreased,solder regions may bridge with each other, causing circuit failure.Additionally, under the fixed ball-size requirement, solder balls musthave a certain size, which in turn limits the number of solder ballsthat can be packed on the surface of a die. Accordingly, IntegratedFan-Out (InFO) packages have been developed.

InFO packages are not suitable for making coils that are used forcertain applications such as wireless charging. Due to the small size ofthe InFO packages, the coils, if made in the InFO packages, would besmall. The mutual inductance between the coils in the InFO packages andthe coils outside of the InFO packages will be low, and cannot meet therequirement of wireless power transfer through magnetic resonance. Onthe other hand, the mutual inductance also cannot be increased byincreasing the number of turns of the coils since this will cause theresistance to be increased, which in turn causes the dramatic reductionof the efficiency of the power transfer.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates the cross-sectional view of an Integrated Fan-Out(InFO) package in accordance with some embodiments.

FIG. 2 illustrates the cross-sectional view of an InFO package includinga sealed air gap in accordance with some embodiments.

FIGS. 3 and 4 illustrate top views of coils and the connecting devicedies in accordance with some embodiments.

FIGS. 5, 9, 11, 13, and 15 illustrate the top views of coils and therespective metal plates and dielectric regions in the metal plates inaccordance with some embodiments.

FIGS. 6-8, 10, 12, 14, and 16 illustrate the structures used forsimulations in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

An Integrated Fan-Out (InFO) package and a coil in the InFO package areprovided in accordance with various exemplary embodiments. The coils inthe InFO packages are referred to as InFO coils throughout thedescription. Some variations of some embodiments are discussed.Throughout the various views and illustrative embodiments, likereference numbers are used to designate like elements.

FIG. 1 illustrates a cross-sectional view of InFO package 100 inaccordance with some embodiments of the present disclosure. InFO package100 includes device die 28 encapsulated in encapsulating material 26. Inaddition, through-conductors 32, which form parts of InFO coil 30, arealso encapsulated in encapsulating material 26. Encapsulating material26 fills the gaps between neighboring through-conductors 32 and the gapsbetween through-conductors 32 and device die 28. Encapsulating material26 may be a polymer-based material, and may include a molding compound,a molding underfill, an epoxy, and/or a resin. The top surface ofencapsulating material 26 is level with the top ends of device die 28,which may be achieved through, for example, Chemical Mechanical Polish(CMP).

InFO coil 30 acts as an inductor, and may have various applicableshapes. For example, FIGS. 3 and 4 illustrate the top views of exemplaryinductors/coils in accordance with some exemplary embodiments. In FIG. 3, through-conductors 32 form a plurality of concentric rings, with theouter rings encircling the inner rings. In FIG. 3 , two rings areillustrated, while any other number of rings (such as 1, 3, or more) isalso contemplated. The rings are partial rings having breaks, whichallow the outer rings to be connected to the inner rings throughbridge(s) 35. The plurality of rings is serially connected to two ports37. The ports of coil 30 are connected to device die 28. In FIG. 4 ,through-conductors 32 are portions of an integrated spiral, which alsohave ports 37. FIG. 4 illustrates that the left port 37 is disconnectedfrom device die 28. In alternative embodiments, the left port 37 mayalso be connected to device die 28, for example, through theredistribution lines 50 and 54 as shown in FIGS. 1 and 2 .

Referring back to FIG. 1 , through-conductors 32 have top surfacessubstantially coplanar with the top surface of encapsulating material26, and bottom surfaces substantially coplanar with the bottom surfaceof encapsulating material 26. Throughout the description, when the term“substantially coplanar” is used, the respective “planar surfaces” maystill have height differences that are within the variation of therespective manufacturing processes.

Device die 28 may be adhered to adhesive film 24 through Die-Attach Film(DAF) 34, which is an adhesive film. DAF 34 may also be omitted, anddevice die 28 is adhered to adhesive film 24 directly. Device die 28 mayhave the function of receiving current from coil 30, rectifying thecurrent, and charging a battery (not shown). Although one device die 28is illustrated, more device dies may be placed over adhesive film 24,which device dies may include a Central Processing Unit (CPU) die, aMicro Control Unit (MCU) die, an Input-output (IO) die, a BaseBand (BB)die, and/or an Application Processor (AP) die.

Device die 28 may include semiconductor substrate 36, which may be asilicon substrate. Integrated circuit devices 38 are formed onsemiconductor substrate 36. Integrated circuit devices 38 may includeactive devices such as transistors and diodes and/or passive devicessuch as resistors, capacitors, inductors, or the like. Device die 28 mayinclude metal pillars 46 electrically coupled to integrated circuitdevices 38. Metal pillars 46 may be embedded in dielectric layer 40,which may be formed of PBO or polyimide, for example. Passivation layer42 is also illustrated, wherein metal pillars 46 may extend intopassivation layer 42. Passivation layer 42 may include silicon nitride,silicon oxide, or multi-layers thereof.

Dielectric layer 48 is formed over encapsulating material 26. Inaccordance with some embodiments of the present disclosure, dielectriclayer 48 is formed of a polymer such as PBO, polyimide, or the like. Inaccordance with alternative embodiments of the present disclosure,dielectric layer 48 is formed of an inorganic material such as siliconnitride, silicon oxide, or the like.

Redistribution Lines (RDLs) 50 are formed to electrically couple tometal pillars 46 and through-conductors 32. RDLs 50 may alsointerconnect metal pillars 46 and through-conductors 32. In addition,RDLs 50 may be used to form bridge 35 (FIG. 3 ) of inductor 30. RDLs 50include metal traces (metal lines) over dielectric layer 48 and viasextending into dielectric layer 48. The vias in RDLs 50 are connected tothrough-conductors 32 and metal pillars 46. In accordance with someembodiments of the present disclosure, the formation of RDLs 50 includesforming a blanket copper seed layer, forming and patterning a mask layerover the blanket copper seed layer, performing a plating to form RDLs50, removing the mask layer, and etching the portions of the blanketcopper seed layer not covered by RDLs 50. RDLs 50 may be formed of ametal or a metal alloy including aluminum, copper, nickel, tungsten,and/or alloys thereof.

Dielectric layer 52 is formed over dielectric layer 48 and RDLs 50.Dielectric layer 52 may be formed using a material selected from thesame candidate materials for forming dielectric layer 48. RDLs 54 areformed to have some portion inside dielectric layer 52, and some otherportions over dielectric layer 52. RDLs 54 may also be formed of a metalor a metal alloy including aluminum, copper, tungsten, and/or alloysthereof. It is appreciated that although in the illustrated exemplaryembodiments, two layers of RDLs (50 and 54) are formed, the RDLs mayhave any number of layers such as one layer or more than two layers.

Dielectric layer 56 is formed over dielectric layer 52 and RDLs 54.Dielectric layer 56 may be formed, for example, using PBO, polyimide, orBCB. Electrical connectors 58 have some portion inside dielectric layer56, and some other portions over dielectric layer 56. Electricalconnectors 58 are formed to electrically connect to RDLs 54. Electricalconnectors 58 may include Under-Bump Metallurgies (UBMs), metal pillars,solder regions, and/or the like. In accordance with some exemplaryembodiments, electrical connectors 58 are electrically connected to aflex Printed Circuit Board (PCB, not shown).

In accordance with some embodiments, ferrite material 60, which may be apre-formed plate, is adhered to a top surface layer such as layer 56.The adhesion may be achieved through adhesive film 62. Ferrite material60 in accordance with some embodiments may include manganese-zinc,nickel-zinc, or the like. Ferrite material 60 has low losses at highfrequencies, and is used to improve the performance (such as the mutualinductance) of InFO coil 30. Ferrite material 60 overlaps a portion ofthe encapsulating material 26. Furthermore, ferrite material 60 overlapsat least a part of InFO coil 30, and may or may not extend beyond theedges of InFO coil 30.

Throughout the description of the present disclosure, the features overadhesive film 24 including electrical connectors 58, device die 28,encapsulating material 26, and through-conductors 32 are in combinationreferred to as InFO package 100. Slot-containing metal plate 18 isunderlying, and is overlapped by, InFO package 100. In accordance withsome embodiments of the present disclosure, InFO package 100 is adheredto slot-containing metal plate 18 through adhesive film 24.

Slot-containing metal plate 18 includes metal plate 22, and dielectricmaterial 20 in the slot of metal plate 22. Throughout the description,reference numeral 20 is used to refer to both the slots inslot-containing metal plate 18 and the dielectric material in the slots.In accordance with some embodiments of the present disclosure, metalplate 22 is formed of a metal or a metal alloy, which is formed ofcopper, aluminum, nickel, chromium, an anodized metal, and/or the like.Dielectric material 20 may fully or partially fill the slot in metalplate 22. In accordance with some embodiments, dielectric material 20 isformed of an organic material such as plastic or polymer, or aninorganic dielectric material such as glass, oxide, ceramic, or thelike. Dielectric material 20 may be transparent or opaque.

Metal plate 22 and dielectric material 20 may have top surfacessubstantially coplanar with each other, and/or bottom surfaces coplanarwith each other. In accordance with some embodiments of the presentdisclosure, metal plate 22 and dielectric material 20 in combinationform a part of a casing, which may be the casing of a mobile phone, atablet, or a computer, for example. The illustrated portion of thecasing is a lower part, and the casing may further include an upper partoverlying, and portions (not shown) on the left side and right of, theillustrated part.

FIG. 2 illustrates InFO package 100 and slot-containing metal plate 18in accordance with alternative embodiments. Slot-containing metal plate18 includes slot 20 therein, wherein slot 20 is an air gap not filledwith solid dielectric materials. Alternatively stated, slot 20 is filledwith air, and hence forming a dielectric region. Dielectric film 16 isused to cover slot 20, wherein dielectric film 16 and adhesive 24 sealslot 20. Throughout the description, when the term “dielectric material20” is referred to, it indicates that dielectric material 20 may be asolid dielectric material or air. Dielectric film 16 may also be formedof a dielectric material such as a plastic, a glass, a ceramic, or thelike.

FIG. 5 illustrates a top view of a part of the structure shown in FIGS.1 and 2 in accordance with some exemplary embodiments, with coil 30 andslot-containing metal plate 18 illustrated. Other materials and regionssuch as dielectric layers 48, 52, and 56, device die 28, and the like asshown in FIGS. 1 and 2 are not illustrated, while they still exist.Dielectric material 20 includes portions 20A and 20B (referred to as adielectric portions or slot portions hereinafter). Dielectric portion20A has a lengthwise direction parallel to a first direction (Xdirection). Portion 20B has a lengthwise direction un-parallel to thelengthwise direction of portion 20A. In accordance with some embodimentsof the present disclosure, the lengthwise direction of portion 20B is inthe Y direction, which is perpendicular to the lengthwise direction ofportion 20A. Portions 20A and 20B may also be neither parallel to norperpendicular to each other. Furthermore, portion 20A may be longer thanportion 20B. Portion 20A and portion 20B are joined with each other toform a cross.

In accordance with some embodiments, slot-containing metal plate 18 hasedges 18A and 18B opposite to each other. Edges 18A and 18B may or maynot be parallel to each other, depending on the shape and the usage ofslot-containing metal plate 18. For example, when slot-containing metalplate 18 is used as the back cover of a mobile phone, the shape ofslot-containing metal plate 18 is determined by the shape of the mobilephone, and edges 18A and 18B may be parallel to each other. Slot portion20A has length L1 and width W1. Length L1 in accordance with theseembodiments is greater than length L3 of coil 30, and is equal to thelength of slot-containing metal plate 18. Width W1 of slot portion 20Ais smaller than length L1, and may be smaller than the width W3 of coil30.

Portion 20B of dielectric material 20 has length L2 and width W2 smallerthan length L2. Furthermore, width W2 may be equal to, greater than, orsmaller than, width W1 of portion 20A. In accordance with someembodiments of the present application, length L2 of portion 20B issmaller than width W3 of coil 30, and width W2 of portion 20B is smallerthan both length L3 and width W3 of coil 30.

Furthermore, portion 20A may extend beyond the edges of coil 30 inopposite X directions. On the other hand, portion 20B may be fully inthe region overlapped by coil 30, and does not extend beyond the edgesof coil 30 (as shown in FIG. 5 ). Alternatively, portion 20B may alsoextend beyond the edges of coil 30 in one or both of the Y directions.In accordance with some exemplary embodiments, the intersection area ofportions 20A and 20B is aligned to coil 30. The center of theintersection area may be aligned to the center of coil 30 to maximizethe magnification effect, as is discussed in subsequent paragraphs.

The InFO coil 30 as shown in FIG. 5 has improved mutual inductance withan external coil 14 (FIG. 1 or 2 ). As shown in FIGS. 1 and 2 , coil 14is placed outside of InFO package 100, and may be outside of the product(such as a mobile phone) in which InFO package 100 is located. Coil 14may be used as a transmitter coil for transmitting energy, for example,while InFo coil 30 is used as a receiver coil for receiving the energytransmitted by coil 14.

FIGS. 6, 7, and 8 illustrate the structures on which simulations areperformed. FIG. 6 illustrates the perspective view of coil 14 and coil30. InFo coil 30 is over coil 14, with no metal plate between InFo coil30 and coil 14. Furthermore, InFo coil 30 is above coil 14, and thecenter of coil 30 is aligned to the center of coil 14. According to thesimulation results, the mutual inductance between InFo coil 30 and coil14 is 123.6 nH. In this setting, the electromagnetic field generated bycoil 14 is transmitted to InFO coil 30 without being blocked.

FIG. 7 illustrates the perspective view of coil 14 and coil 30, on whicha simulation is performed. InFo coil 30 is over and aligned to coil 14,with a large metal plate 22 between (and aligned to) InFo coil 30 andcoil 14. Metal plate 22 has no slot therein, and hence fully blocks theelectromagnetic field generated by coil 14 from being transmitted tocoil 30. According to the simulation results, the mutual inductancebetween InFo coil 30 and coil 14 is 0.1 nH, indicating that essentiallyno mutual inductance exists between InFo coil 30 and coil 14.Accordingly, InFO coil 30 and coil 14 cannot be used for wireless powertransfer when an un-slotted metal plate (such as an un-slotted metalback cover of a phone) is placed therebetween. The results obtained fromFIGS. 6 and 7 are used as benchmarks to compare the performance of otherstructures in accordance with various embodiments of the presentdisclosure.

FIG. 8 illustrates the top view of coil 14 and coil 30, on which asimulation is performed. InFo coil 30 is over coil 14, withslot-containing metal plate 18 (same as what is shown in FIG. 5 ) placedbetween InFo coil 30 and coil 14. According to the simulation results,the mutual inductance between InFo coil 30 and coil 14 is 192 nH. It isnoted that this mutual inductance is greater than the mutual inductanceobtained from FIG. 6 (123.6 nH). This indicates that the cross-shapedslot as shown in FIG. 5 not only allows the full passing-through of theelectromagnetic field, the electromagnetic field is also magnified,which means better efficiency in the wireless charging.

Referring again back to FIG. 5 , if the widths W1 and/or W2 of slot 20are too big, for example, equal to or greater than width W3 of coil 30,the mutual inductance would be reduce to the mutual inductance (123.6nH) obtained from FIG. 6 . Accordingly, keeping widths W1 and/or W2 nottoo big is beneficial for increasing the mutual inductance. On the otherhand, widths W1 and/or W2 cannot be too small since the slots with verysmall widths W1 and/or W2 do not allow the electromagnetic field to passeasily, and the mutual inductance may degrade to the mutual inductanceobtained in FIG. 7 . In accordance with some embodiments, widths W1and/or W2 are equal to or greater than the wavelength of the powerapplied on coil 14.

FIG. 9 illustrates a top view of a part of the structure shown in FIGS.1 and 2 in accordance with some exemplary embodiments, with coil 30 andslot-containing metal plate 18 illustrated. Dielectric material 20includes central bulk portion 20C and elongated portion 20D, which isjoined to bulk portion 20C to form a continuous dielectric region. Bulkportion 20C is overlapped by coil 30 (when viewed in the cross-sectionalview). In accordance with some exemplary embodiments. Bulk portion 20Cis smaller (in the top view as in FIG. 6 ) than coil 30. Furthermore,all edges of bulk portion 20C may be rescinded from the respective edgesof coil 30, and hence coil 30 fully overlaps bulk portion 20C.Alternatively stated, coil 30 extends beyond the edges of bulk portion20C. In accordance with some exemplary embodiments, the center of theintersection area of portions 20A and 20B is aligned to the center ofcoil 30. The top view of coil 30 may have a circular shape, arectangular shape, a hexagonal shape, an octagonal shape, or anotherapplicable shape.

Elongated portion 20D has a first end connected to bulk portion 20C, anda second end extending beyond the respective edge (the illustrated upperedge) of coil 14. In accordance with some embodiments, as illustrated inFIG. 9 , elongated portion 20D extends to edge 18A of slot-containingmetal plate 18. In accordance with alternative embodiments, elongatedportion 20D extends beyond the respective edge (the illustrated upperedge) of coil 14, and does not reach edge 18A. Width W1 of elongatedportion is smaller than width W3 of coil 30 in accordance with someembodiments.

FIG. 10 illustrates the top view of coil 14 and coil 30, on which asimulation is performed. InFo coil 30 is over coil 14, withslot-containing metal plate 18 (similar to what is shown in FIG. 9 , andwith an additional slot) placed between InFo coil 30 and coil 14.According to the simulation results, the mutual inductance between InFocoil 30 and coil 14 is 240.4 nH. The results are similar if theadditional slot is not added. It is noted that this mutual inductance isgreater than the mutual inductance obtained from FIG. 6 (123.6 nH). Thisindicates that the slot as shown in FIG. 9 has the effect of magnifyingthe electromagnetic field, which means better efficiency in the wirelesscharging.

Referring again back to FIG. 9 , if portion 20C is too large, forexample, with sizes equal to or greater than the size of coil 30, themutual inductance would be close to the mutual inductance obtained fromFIG. 6 . Accordingly, keeping the size of portion 20C to be smaller thanthe size of coil 30 is beneficial for increasing mutual inductance.

FIG. 11 illustrates a top view of a part of the structure shown in FIGS.1 and 2 in accordance with some exemplary embodiments, with coil 30 andslot-containing metal plate 18 illustrated. The shape of dielectricmaterial 20 in accordance with these embodiments is similar to that inFIG. 5 , except no shorter portion exists. Dielectric material 20extends to both edges 18A and 18B of slot-containing metal plate 18.Dielectric material 20 is in a single stripe-shaped slot, which extendsfrom edge 18A to opposite edge 18B of slot-containing metal plate 18.Dielectric material 20 extends beyond the edges of coil 30 in opposite Xdirections, and length L1 of dielectric material 20 is greater thanlength L3 of coil 30. On the other hand, width W1 of dielectric material20 is smaller than width W3 of coil 30.

FIG. 12 illustrates the top view of coil 14 and coil 30, on which asimulation is performed. InFo coil 30 is over coil 14, withslot-containing metal plate 18 as shown in FIG. 11 placed between InFocoil 30 and coil 14. According to the simulation results, the mutualinductance between InFo coil 30 and coil 14 is 137.9 nH. It is notedthat this mutual inductance is greater than the mutual inductanceobtained from FIG. 6 (123.6 nH). This indicates that the slot as shownin FIG. 11 also has the effect of magnifying the electromagnetic field,which means better efficiency in the wireless charging.

Referring again back to FIG. 11 , if width W1 of dielectric material 20is too large, for example, greater than width W3 of coil 30, the mutualinductance would be reduced to the mutual inductance obtained from FIG.6 . Accordingly, keeping width W1 to be smaller than width W3 of coil 30is beneficial for increasing the mutual inductance. On the other hand,width W1 cannot be too small since the slots with very small width W1 donot allow the electromagnetic field to pass easily, and the mutualinductance may degrade to the mutual inductance obtained in FIG. 7 .

FIG. 13 illustrates a top view of a part of the structure shown in FIGS.1 and 2 in accordance with some exemplary embodiments, with coil 30 andslot-containing metal plate 18 illustrated. The shape of dielectricmaterial 20 in accordance with these embodiments is similar to that inFIG. 11 , except dielectric material 20 extends to edge 18B and does notextend to edge 18A. Similarly, dielectric material 20 extends beyond theedges of coil 30 in both X directions, and length L1 of dielectricmaterial 20 is greater than length L3 of coil 30. On the other hand,width W1 of dielectric material 20 is smaller than width W3 of coil 30.

FIG. 14 illustrates the top view of coil 14 and coil 30, on which asimulation is performed. InFo coil 30 is over coil 14, withslot-containing metal plate 18 as shown in FIG. 13 placed between InFocoil 30 and coil 14. According to the simulation results, the mutualinductance between InFo coil 30 and coil 14 is 138.2 nH. It is notedthat this mutual inductance is greater than the mutual inductanceobtained from FIG. 6 (123.6 nH). This indicates that the slot as shownin FIG. 13 has the effect of magnifying the electromagnetic field, whichmeans better efficiency in the wireless charging. The width W1 andlength L1 of dielectric material 20 have similar requirement as in FIG.11 .

FIG. 15 illustrates a top view of a part of the structure shown in FIGS.1 and 2 , with coil 30 and slot-containing metal plate 18 illustrated inaccordance with some exemplary embodiments. The shape of dielectricmaterial 20 in accordance with these embodiments is similar to that inFIG. 11 , except dielectric material 20 is fully encircled by metalplate 18, and does not extend to either one of edges 18A and 18B.Similarly, dielectric material 20 extends beyond the edges of coil 30 inboth X directions, and length L1 of dielectric material 20 is greaterthan length L3 of coil 30. On the other hand, width W1 of dielectricmaterial 20 is smaller than width W3 of coil 30.

FIG. 16 illustrates the top view of coil 14 and coil 30, on which asimulation is performed. InFo coil 30 is over coil 14, withslot-containing metal plate 18 as shown in FIG. 15 placed between InFocoil 30 and coil 14. According to the simulation results, the mutualinductance between InFo coil 30 and coil 14 is 29.8 nH. It is noted thatthis mutual inductance is smaller than the mutual inductance obtainedfrom FIG. 6 (123.6 nH). This indicates that the slot as shown in FIG. 13allows the electromagnetic field to pass through, although with reducedmagnitude. Further comparing the results in FIGS. 8, 10, 12, 14, and 16, it is observed that allowing the dielectric material (slot) in themetal plate to extend to an edge of the metal plate may lead to improvedmutual inductance, while not allowing the dielectric material (slot) toreach the edges results in degraded mutual inductance.

The embodiments of the present disclosure have some advantageousfeatures. By forming slot(s) in metal plates, electromagnetic field maypass through the metal pate, and the mutual inductance between the InFOcoil and an external coil is improved. Furthermore, the mutualinductance may be magnified, resulting in the improvement in wirelesscharging efficiency.

In accordance with some embodiments of the present disclosure, astructure includes an encapsulating material, and a coil including athrough-conductor. The through-conductor is in the encapsulatingmaterial, with a top surface of the through-conductor substantiallycoplanar with a top surface of the encapsulating material, and a bottomsurface of the through-conductor substantially coplanar with a bottomsurface of the encapsulating material. A metal plate is underlying theencapsulating material. A slot is in the metal plate and filled with adielectric material. The slot has a portion overlapped by the coil.

In accordance with some embodiments of the present disclosure, astructure includes an encapsulating material, a device die encapsulatedin the encapsulating material, and through-conductors encapsulated inthe encapsulating material. The through-conductors form parts of a coilelectrically coupled to the device die. The structure further includes ametal plate with a portion overlapped by the coil, wherein the metalplate extends beyond edges of the coil. A dielectric material penetratesthrough the metal plate. The dielectric material includes a firstelongated portion having a first lengthwise direction parallel to afirst direction. The first elongated portion includes a first portionoverlapped by the coil, and a second portion un-overlapped by the coil.The dielectric material further includes a second elongated portionhaving a second lengthwise direction parallel to a second direction,with the second direction unparallel to the first direction. The secondelongated portion is joined to the first elongated portion, and isoverlapped by the coil.

In accordance with some embodiments of the present disclosure, astructure includes an encapsulating material, a device die encapsulatedin the encapsulating material, and through-conductors encapsulated inthe encapsulating material. The through-conductors form parts of a coilelectrically coupled to the device die. The structure further includes ametal plate with a portion overlapped by the coil. The metal plateextends beyond edges of the coil. A dielectric region penetrates throughthe metal plate. The dielectric region includes a bulk portionoverlapped by the coil, and an elongated portion connected to the bulkportion. The elongate portion is narrower than the bulk portion. Theelongate portion includes a first portion overlapped by the coil, and asecond portion extending beyond an edge of the coil.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A structure comprising: an encapsulant; a devicedie in the encapsulant; through-conductors in the encapsulant, whereinthe through-conductors form parts of a coil, and the coil iselectrically coupled to the device die; a metal plate having a portionoverlapped by the coil, wherein the metal plate extends beyond edges ofthe coil, and wherein the metal plate is electrically insulated from thecoil; and a dielectric region in the metal plate and comprising aportion overlapped by the coil, wherein the dielectric region comprises:a strip portion having a uniform first width; and an enlarged portionjoined with the strip portion, wherein the enlarged portion has a secondwidth greater than the uniform first width.
 2. The structure of claim 1,wherein the metal plate extends laterally beyond the coil in all lateraldirections.
 3. The structure of claim 1, wherein the dielectric regioncomprises an organic material.
 4. The structure of claim 1, wherein thedielectric region comprises an inorganic material.
 5. The structure ofclaim 1 further comprising a dielectric film between, and contactingboth of, the metal plate and the coil.
 6. The structure of claim 1further comprising redistribution lines over the coil and theencapsulant, wherein the redistribution lines electrically connect thedevice die to the coil.
 7. The structure of claim 1, wherein the stripportion has a lengthwise direction and a widthwise directionperpendicular to the lengthwise direction, and wherein both of theuniform first width and the second width are measured in the widthwisedirection.
 8. The structure of claim 1, wherein the enlarged portion hasa circular top-view shape.
 9. A structure comprising: an encapsulant; adevice die encapsulated by the encapsulant; through-conductorsencapsulated in the encapsulant, wherein the through-conductors formparts of a coil, and the coil is electrically coupled to the device die;a metal plate underlying the coil, wherein the metal plate laterallyextends beyond edges of the coil; and a dielectric material penetratingthrough the metal plate, wherein the dielectric material comprises: afirst portion having a lengthwise direction parallel to a firstdirection, wherein the first portion has a first width; and a secondportion having a second width greater than the first width, wherein thesecond portion has an end spaced apart from a respective nearest edge ofthe metal plate, and wherein both of the first width and the secondwidth are measured in a widthwise direction perpendicular to thelengthwise direction.
 10. The structure of claim 9, wherein the firstportion and the second portion are continuously joined with each other.11. The structure of claim 9, wherein the first portion of thedielectric material comprises a first sub portion overlapped by thecoil, and a second sub portion extending laterally beyond the coil. 12.The structure of claim 11, wherein the first portion of the dielectricmaterial further comprises a third sub portion extending laterallybeyond the coil, wherein the second sub portion and the third subportion are on opposing sides of the coil.
 13. The structure of claim 9,wherein the first portion extends to an edge of the metal plate.
 14. Thestructure of claim 9, wherein the second portion has a first centersubstantially vertically aligned to a second center of the coil.
 15. Thestructure of claim 9, wherein the metal plate extends laterally beyondthe coil in all lateral directions.
 16. A structure comprising: amolding compound; through-conductors encapsulated in the moldingcompound, wherein the through-conductors form parts of a coil; and adielectric region comprising: an elongated portion having a uniformwidth, wherein the elongated portion comprises a first part overlappedby the coil, and a second part extending beyond an outmost edge of thecoil; and an enlarged portion directly underlying the coil, wherein theelongated portion and the enlarged portion are joined with each other.17. The structure of claim 16, wherein an entirety of the enlargedportion is underlying the coil.
 18. The structure of claim 16, wherein afirst center of the enlarged portion is substantially vertically alignedto a second center of the coil.
 19. The structure of claim 16, whereinthe dielectric region comprises an air gap.
 20. The structure of claim16 further comprising a metal plate, wherein a first top surface of thedielectric region is coplanar with a second top surface of the metalplate, and wherein a first bottom surface of the dielectric region iscoplanar with a second bottom surface of the metal plate.